Annealing magnetic material



w; J. WOOLDRIDGE.

ANNEALING MAGNETIC MATERIAL.

APPLICATION FILED DEC. 17, I918- Patented Feb. 24, 1920.

l a W O 7 W W 4 K. a 4 w ..v m F l W l Inventor". William J.Wooldridg e, in b g His flttorneg.

- UNITED STATES PATENT OFFICE.

WILLIAM Er. WOOLDRIDGE, OF rI T sFIE Ln,

MASSACHUSETTS, ASSIGNOR To GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ANNEALING MAGNETI MATERIAL:

e Application filed December f7,1918.-S eria1No. 267110. F v

To all whom it may concern:

e Be it known that I, WILLIA J. Woo L DRIDGE, a citizen of the United States, residing at Pitts'field, in the county of Berkshire, State of Massachusetts, have invented certain new and useful Improvements in Annealing Magnetic Materials, of which the following is a specification. a

.My invention has reference to improvements in the process of annea-lin magnetic material, mainly silicon steel in s eet form, and it consists'in exposing and supporting the sheet material while subjected to the annealing temperature, in annealing pots or otherwise, in such manner as to give -.free access of heat radiation to and circulation of evolved gases over the material on all sides, whereby the sheets are annealed uniformly through their whole extent.

Magnetic sheetfmaterial has heretofore. been annealed by placing the sheets in well known annealing pots, stacked flatw'ise one above the other and each in contact with the preceding and succeeding sheets" and each under the pressure of the weight of the np per pile. In this manner all sheets are partially shielded from the direct heat radiation from the walls of the annealinglpot, and the gases which are evolved from the 30 sheets in the pot or enter the .pot from the furnace cannot freely circulate over' the faces of the material. The consequence is that the annealing effect is limited to more or less irregular portions'near the edges of the sheets, while the more central portions are poorly, a-ndin many cases not at all, anne'aled'. By my invention this detrimental effect of the stacking of the sheets'fone on top of the ot'her is avoided, and practically uniform and effective annealing all throughout the sheets is achieved. This result has heretofore been attained by assembling and maintaining the whole; Charge of sheets loosely face to face with small but sensible spaces between them; andsresting edgewi'se on the floor of the annealing pot, and subjecting the potto'the requisite temperature. But while in this manner the sheets became well annealed, they buckled considerably when softened by the high temperature to which they had to be raised, under the pres- ,7 sure ofthe weight of each sheet upon itssupporting edge. 'Moreover,'the assembling of-a great number of sheets which consti tute the charge of a pot, in the "manner in- .sheets in the-old processes.

.dicated, and the maintenance of the assemblage, has been found to be uncertain, diffi- "cult and time consuming, so" that in commer- Specification of Letters ream. P tented Feb. 24;, 1920. I

invention is an improvement upon the proce ess just described, whereby the disadvantag'espoi-nted out are avoided and an efiicient' commercial practice issecured. 5 In the accompanying drawing; the old practice of piling the sheets flatwise on top of each other, its result, and the present inis a vertical section of an annealing pot with the material to be annealed piled up flatventions are illustrated as follows: Figure 1 wise in the old conventional manner; Fig. 2 I

is aface View of one sheet of a stack subjected to the old practice, showingby appropriate shading the resulting imperfect annealing; Fig. 3 is a vertical section of an annealing pot with'bundles of sheets arranged in the same in accordance with one f of the practices of my invention; Fig. 4 is.

a like section at right angles to that shown in Fig. 3 of an annealing pot with bundles of sheets arranged in the same in accordance with another practice of my invention, and Fig. 5 is a perspective-yiew of a bundle of sheets, which in the practiceof my. in-

vention is a unit corresponding to the single 5 Referring now to Fig. 1, the ordinary nealing 0t 10. with its legs 11 and its cover 12, has t e sheets 13, stacked up, as indicated, "flatwiseoneon top of the other with no "ap preciable spaces between them, so that each sheet covers every preceding one and is in .turn covered by the succeeding one, and the heat radiation from the walls of the pot as well as the'gases evolved can only reach a comparativelysmall portion of each sheet inside of its .edge', as --indicated by shading 14 in Fig. 2, while the central portion of the C to improve itsmagnetic characteristic-s, its, hysteresis and permeability, and it will be seen that when the sheets upon which the effect of the old process is indicated 'in Fig.

nealing pots there is usually a series of holes all along the walls of the same, whereby the gases developed inside the pot are allowed to circulate both within the pot and also between the pot and the furnace. This rangement shown in Fig. 3 may be used.

has been found to be of considerable advantage. But the circulation which these holes would aiiord: can only benefita small and irregular portion of each sheet, as indicated in Fig. 2 by the shading 14.

In accordance with my invention the ar- The annealing pot is the same as in Fig. 2,

'- but the arrangement of the sheets within the pot diflers' from the old practice. Here the mass ofthe sheetsis shown to be divided into small bundleslfi, each bundle comprising a limited number of sheets, placed face to face and loosely held togetherby a'number of'clips 17, of band iron. These clips are liberally spaced and they do not forcibly press the sheets together, but they prevent the shifting of the sheets and make of each bundle a unit, the elements of which, the sin lev sheets, are in loose contact and still su ciently separated by sensible spaces through which the heat radiation and the evolved gases can pass. Each of these bundles 16, is arranged vertically in the pot, with its lower edge-raised from the floor of the pot by the thickness of the clips 17, and the successive bundles .are spaced from each other by the same clips. The lower edge of each bundle has only to sustain its own weight and no bundle presses upon another,

so that the small spaces between the individual sheets are maintained and each bundle; is laterally braced by the others. With the arrangement shown 1n Fig. 3-, the conditions ofithe individual sheets as respects the access to the same of heat radiation and circu- "lation ofthe evolved gases and of the gases which enter the pot by the vent holes 15 is largely promoted, and is practically the same as if the sheets, standing on ed e, were all loosely held together by any kin oflateral props. There i s, however, this important practical diflerence between the two arrangements, that, the division of the whole charge ofa pot into bundles, in accordance for extensive and uniform commercial practice, whereas the arrangement of the whole charge in one mass of a multitude of loose sheets, is difficult and vexatious, and allows lesgch sheet to buckle and have its lower edge Another practicalmanner of realizing my is spacedfrom the next succeeding or pro ceding section by strips 17 of band-iron,

so that each section as a whole is free to the access of heat radiation and to the circulation of evolved gases, and of the gases which enter by the vent holes 15 while each individual sheet is held to the nextpreCading one by lightpressure at the separating strips and there is barely any pressure between the successive strips. I have found by continued'commercial use of this arrangement that the sheets become well annealed allover, so that this form of my invention is as effective as the arrangement shown in Fig. 3, or as the arrangement heretofore referred to, where the whole charge is put into the pot edgewise in one lot of a multitude of loose sheets.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. The process of annealing a mass of sheets of magnetic material, which consists in dividin the mass into bundles or sections'of a llmited number of loosely contacting sheets, assembling the bundles or sections in an annealing pot in such manner so- I as to' leave the faces of the sheets and of the bundles or sections free to the access of radiant heat and to the sweep of gases evolved in the pot and outside of the same, and subjecting the assembled bundles or sections to.

a suitable annealing temperature.

' 2. The process of annealing a mass of sheets of magnetic material, which consists in dividing the mass into loose sections or bundles of a limited number of sheets, piling the sectionsor bundles fiatwise in an-annealing pot with sensible spaces between the same, and promoting the sweep of internally and externally evolved. gases over the bun dles and sheets while subjecting the whole to a suitable annealing temperature.

In.witness whereof I have hereunto set m hand this 14th. day of December, 1918. with my invention, renders the procedure fig;

WILLIAM J. WOOLDRIDGE. 

